The next presidential election is three years away, but Turning Point USA already knows it wants Vice President JD Vance as the Republican nominee. Erika Kirk, leader of the powerful conservative youth organization, endorsed him on opening night of its annual AmericaFest convention, drawing cheers from the crowd. But the four-day gathering revealed more peril than promise for Vance or any other potential successor to President Donald Trump, and the tensions on display foreshadow the waters that they will need to navigate in the coming years. After a weekend of debates about whether the movement should exclude figures such as...